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Lenz's law

(Encyclopedia)Lenz's law, physical law, discovered by the German scientist H. F. E. Lenz in 1834, that states that the electromotive force (emf) induced in a conductor moving perpendicular to a magnetic field tends...

Jocelin de Brakelond

(Encyclopedia)Jocelin de Brakelond jŏsˈlĭn də brākˈlŏnd [key], fl. 1200, English chronicler, a monk of Bury St. Edmunds. His chronicle of St. Edmund's Abbey, covering the years 1173–1202, is written in a s...

Leutze, Emanuel

(Encyclopedia)Leutze, Emanuel loitˈsə [key], 1816–68, American historical painter, b. Germany. In 1859 he settled in the United States, working in Washington, D.C., and New York City. His pictures are chiefly E...

ratchet and pawl

(Encyclopedia)ratchet and pawl, mechanical device that permits motion in one direction only. The ratchet is usually a wheel with slanting teeth. The pawl is a lever tangential to the wheel with one end resting on t...

motor, electric

(Encyclopedia)CE5 Motor: In the AC motor, current fed to the conducting loop of wire causes it to rotate in the magnetic field, thus turning the shaft on which the loop is mounted. In the DC motor, the direction...

Van Dyck, Sir Anthony

(Encyclopedia)Van Dyck or Vandyke, Sir Anthony both: văn dīk [key], 1599–1641, Flemish portrait and religious painter and etcher, b. Antwerp. In 1618 he was received as a master in the artists' guild, but even ...

Democritus

(Encyclopedia)Democritus dĭmŏkˈrĭtəs [key], c.460–c.370 b.c., Greek philosopher of Abdera; pupil of Leucippus. His theory of the nature of the physical world was the most radical and scientific attempted up ...

airfoil

(Encyclopedia)airfoil, surface designed to develop a desired force by reaction with a fluid, especially air, that is flowing across the surface. For example, the fixed wing surfaces of an airplane produce lift, whi...

Cunningham, Imogen

(Encyclopedia)Cunningham, Imogen, 1883–1976, American photographer, b. Portland, Oreg. Cunningham began taking pictures in 1901. After study abroad she opened a studio in Seattle in 1910 and for six decades produ...

Dabo, Leon

(Encyclopedia)Dabo, Leon däˈbō [key], 1868–1960, American painter, b. Detroit. He worked with John La Farge, studied in Paris under Puvis de Chavannes, and was influenced by Whistler and by Japanese landscape ...